1. Field of the Invention
The present invention relates generally to energy efficient wall and closure systems for minimizing loss of thermal energy from thermal treatment chambers of high temperature furnaces and the like, such as are used in industry to reheat slabs, billets and blooms of steel or the like. Features of the invention are well suited for use in constructing movable panels that typically are used as doors to selectively close furnace openings to periodically permit entrance into and/or exit from treatment chambers of sizable bodies of steel that need to be uniformly reheated to enable the steel to be properly worked, for example by forging.
More particularly, features of the present invention relate to such diverse subject matter as: methods of forming elongate cast refractory members that are adapted for direct, rigid connection to an external frame for cooperating with other refractory insulation to provide frame-supported insulated panels; methods of constructing frame-supported insulated panels that incorporate arrays of elongate, cast refractory members that extend in side-by-side relationship with bodies of fiber-type refractory compressed between adjacent pairs of the cast refractory members; and to frame-supported insulated panels that include compressively sandwiched arrays of cast refractory members that advantageously cooperate to define interior surface portions which have a capability to store impingent heat energy from a high temperature treatment chamber and to re-radiate stored heat energy back into the treatment chamber.
2. Prior Art
Large industrial apparatus for effecting thermal treatment of sizable charges of material that are admitted sequentially to and discharged sequentially from a thermal treatment chamber often are provided with inlet and outlet openings located on opposite sides of the treatment chamber. It is well known to provide such apparatus with insulated closures of various types for selectively opening and closing the inlet and outlet openings.
For example, in the steel industry it is well known to utilize what is referred to as a "reheat furnace" to sequentially heat large, pre-formed bodies of steel to desired temperatures to enable the heated bodies to be "worked" or otherwise formed, typically by rolling or by forging. A reheat furnace characteristically has a treatment chamber that is capable of receiving a plurality of large steel bodies such as slabs, billets or blooms of steel. The bodies of steel to be heated typically are fed through the treatment chamber relatively slowly in a direction of travel that extends from an inlet or entry opening located on one side of the treatment chamber to an outlet or exit opening located on an opposite side of the treatment chamber.
The referenced Parent Case and the referenced Door Patents describe and illustrate selected features of steel reheat furnaces, and disclose inventions that address needs that are present in industry for insulated panel assemblies that are adequately rugged and heat resistant to permit their being used as furnace closures, typically as entry and exit doors for steel reheat furnaces. All three of these referenced cases disclose the use of fiber-type refractory insulation to line and/or define interior surface portions of furnace doors. Moreover, the two referenced Door Patents disclose furnace door embodiments that employ compressed stacks of fiber-type refractory bodies that are securely anchored to and supported by exterior frames.
While compressed stacks of fiber-type refractory bodies supported by exterior frames are well suited to serve the needs of furnace treatment chambers that operate at or below about 2,400 degrees Fahrenheit, present-day materials from which compressible fiber-type refractory bodies are formed tend not to provide insulated panel assemblies that are characterized by long service life if directly exposed for substantial periods of time to treatment chamber temperatures that exceed about 2,400 degrees Fahrenheit. Thus, while fiber-type refractory materials may become available at some time in the future that can be substituted for present-day materials and that will perform durably and offer good service life even when exposed for substantial periods of time to temperatures exceeding about 2,400 degrees Fahrenheit, at present, the environments within which features of the referenced Door Patents are most suitably deployed are those wherein temperatures do not exceed about 2,400 degrees Fahrenheit.
Another concern that arises when relatively large interior surface areas of fiber-type refractory panels are exposed for significant periods of time to high temperature environments is the tendency of fibers from the refractory to become airborne. As a general rule, the greater the exposed surface area of fiber-type refractory, the greater is the concern that minuscule pieces of fiber may become airborne. Furthermore, the higher the temperature to which the refractory is exposed, the more rapidly the fiber-type refractory tends to deteriorate so as to present conditions that are increasingly susceptible to tiny pieces of fiber breaking away and becoming airborne.
Still another concern (that inherently is present to some degree in almost all applications wherein refractory fiber-type insulation is used to form wall portions of a high temperature treatment chamber) is referred to by the term "shadow effect." Whereas wall portions that are formed from refractory brick readily store and re-radiate impingent heat energy, wall portions formed from refractory fiber-type insulation do not. Thus, while re-radiation of heat energy from refractory brick-lined walls will assist in maintaining nearby portions of steel bodies at desired high temperatures, refractory fiber-lined walls tend not to re-radiate heat energy and therefore tend to permit nearby portions of uniformly heated bodies of steel to cool undesirably, just as if a "shadow" had been cast over such portions to shield them from a source of heat energy (hence the origin of the term "shadow effect").
The "shadow effect" of such refractory fiber-type insulation as lines the interior surface of an exit closure of a steel reheat furnace tends to pose a particular concern when bodies of steel need to be discharged from a steel reheat furnace in a uniformly heated state, for example for use in forging processes. Success in carrying out forging processes depends in significant measure on supplying steel that is uniformly heated to within a relatively narrow range of desired working temperatures. If the "shadow effect" of fiber-type refractory causes a slab of re-heated steel to lose its uniform working temperature, the heated slab may have to be shunted aside until it can be put through still another re-heat cycle.
Despite prior proposals, a need remains for frame-supported insulated panels that alleviate "shadow effect" concerns, that minimize airborne fiber concerns, and that function well in high temperature environments wherein temperatures are maintained within the range of about 2400 to about 2800 degrees Fahrenheit.